I have used a pet buggy for my Japanese Chins & know of other owners that have found them useful for ill or elderly dogs. I bought mine years ago. It was a special offer and I think it was about £20. A cavalier could lie down in it and it has mesh netting that can be zipped up to enclose the buggy completely, although that would be no barrier to a determined dog of any size.
I don't use the buggy at the moment and would be happy to lend it short term to anyone who needs it. They would need to collect and deliver it back to Hatfield.
Cavaliers......Tommy Tuppence 2000-2012 and a half share of Faith.
Japanese Chins.... Dandy, Benny, Bridgette and Hana.